This is an invention to accelerate coloring and improve sweetness of citrus fruits by obtaining extracts containing effective ingredients from water solutions of mycelium nutrient medium and tissue-medium of edible fungus belonging to the genus Basidiomycetes and, after diluting with water, spraying this over the surface of the leaves to accelerate coloring and increasing sugar content. As accelerating coloring of citrus fruits is carried out with the prerequisite or early shipment, which will be advantageous in marketing, it is an important facet in the cultivation of citrus fruits. Not only does it also improve the quality from the standpoint of taste and sweetness, it is also an important process from the viewpoint of preventing deterioration in quality. In the past, several types of chemicals were developed for this purpose. For instance, ethylene was used to accelerate coloring. However, in addition to infuring the tree and increasing defoliation, problems were also involved in relation to safety. There were also examples of sulfur being employed as a sweetening agent but again there were problems in relation to safety and its detrimental effect on the tree. This method is therefore not in general use. In addition, chemicals capable of accelerating coloring and improving sweetness at the same time have yet to be developed. However, as a result of various research projects carried out over many years in relation to mecelium of edible fungus belonging to the genus Basidiomydetes by the inventor, numerous inventions were made in relation to methods of extracting chemical ingredients contained in the mycelium. On one hand, it was discovered that the extract of mycelium nutrient medium and tissue-medium contained a substance having cytokinin activity. This invention was made when the extract was sprayed over the citrus fruits as in the foregoing and it was accidentally discovered that it was extremely effective in accelerating coloring and increasing sweetness.